<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <p id="test">hello world</p>
    <script>
    var test=document.getElementById("test");
    var h1=document.createElement("h1");
    h1.innerHTML="前面";
    test.before(h1);
    var h2=document.createElement("h2");
    h2.innerHTML="后面";
    test.after(h2);
    </script>
</body>
</html>